Self-adhesive reinforced foam gasket

ABSTRACT

A self-adhesive reinforced foam gasket comprising a release liner having an upper surface which is a release surface, a layer of pressure sensitive adhesive applied to the release surface, a layer of flexible polymeric film, preferably polyester film, applied to the pressure sensitive adhesive layer, and a layer of flexible foam, preferably closed cell PVC flexible foam, thermally bonded to the flexible polymeric film layer. A length of material for die-cutting the gasket therefrom is provided, along with a method of making the length of material. The gasket may be used in automobiles and other applications.

This is a divisional of U.S. patent application Ser. No. 09/198,659,filed Nov. 24, 1998 now U.S. Pat. No. 6,190,751.

FIELD OF THE INVENTION

The invention relates generally to foam gaskets and more particularly toa self-adhesive reinforced foam gasket.

DESCRIPTION OF RELATED ART

Common weatherstripping for use in the home is well-known. This productis frequently a thick but narrow layer or strip of closed cell plasticflexible foam with a layer of pressure sensitive adhesive on one surfaceprotected by a release liner. The release liner is removed and theweatherstripping is adhered or stuck around a door frame, a windowframe, etc. to seal out wind, noise and moisture. This weatherstrippingwith adhesive and release liner is frequently produced in a very widesheet (such as 5 feet wide) which is coiled up and slit into a series ofthin coils for sale to the consumer. It is believed that in the autoindustry it has been known to take a five foot wide sheet of thisweatherstripping material, slit it and die cut gaskets in circles,rectangles, etc. for use as a self-adhesive non-reinforced foam gasketin automotive applications such as seals around interior audio speakers,seals around cut-outs in the dash for air conditioning ducting, etc. Oneproblem is that this product easily stretches or distorts during theapplication process and the fit is poor or imperfect.

To address this problem a prior art product as illustrated in FIG. 1 hasbeen used in the auto industry. FIG. 1 shows a self-adhesive reinforcedfoam gasket 10 comprising a thick layer of closed cell PVC flexible foam12, a layer of pressure sensitive adhesive 13, a layer of flexiblepolyester film 14 (such as Mylar), a layer of pressure sensitiveadhesive 16, and a release liner 20 comprised of release paper 22 with asilicone release coating 18.

This product has been produced in wide, approximately five foot, sheetsby providing a release liner 20 having a release surface provided byrelease coating 18, to which is applied a layer of pressure sensitiveadhesive 16. A layer of polyester film 14 is then applied to thepressure sensitive adhesive layer 16. On top of polyester film layer 14is applied pressure sensitive adhesive layer 13, to which is laminated,at room temperature, a previously produced thick layer of closed cellPVC foam 12. In the prior art this product was then die-cut to providereinforced self-adhesive foam gaskets which were used in the autoindustry generally as described above. The polyester film layerprevented the stretching which was a problem with the conventionalweatherstripping. The problem with this polyester film-reinforcedproduct is that it is expensive and laborious to produce, and the closedcell PVC foam layer 12 is attached to the polyester film layer 14 by alayer of pressure sensitive adhesive 13, which is not a sufficientlysecure way to attach the closed cell PVC foam layer to the polyesterfilm layer. Also, plasticizer in the PVC foam layer 12 tends to bleedthrough to the adhesive layer 13 and degrade and turn gummy the pressuresensitive adhesive layer 13.

There is a need for a self-adhesive reinforced foam gasket whichovercomes the deficiencies in the prior art and a method to produce suchan improved product.

SUMMARY OF THE INVENTION

A self-adhesive reinforced foam gasket is provided, comprising a releaseliner having an upper surface which is a release surface, a layer ofpressure sensitive adhesive applied to the release surface, a layer offlexible polymeric film applied to the pressure sensitive adhesivelayer, and a layer of flexible foam thermally bonded to the flexiblepolymeric film layer. The gasket has a shape such that it may be usedeffectively as a self-adhesive foam gasket. A length of materialsuitable for die-cutting a self-adhesive reinforced foam gaskettherefrom is also provided. The material comprises a release linerhaving an upper surface which is a release surface, a layer of pressuresensitive adhesive applied to the release surface, a layer of flexiblepolymeric film applied to the pressure sensitive adhesive layer, and alayer of flexible foam thermally bonded to the flexible polymeric filmlayer. The length of material is at least 8 inches wide and 20 feetlong. A method of making the length of material is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, cross-sectional view of a prior art self-adhesivereinforced foam gasket.

FIG. 2 is a top view of a self-adhesive reinforced foam gasket of thepresent invention.

FIG. 3 is a schematic, cross-sectional view of the gasket of FIG. 2taken along line 3—3.

FIG. 4 is a top or plan view of a length of material according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

As used herein, parts are parts by weight and percents are weightpercents unless otherwise indicated or apparent. When a preferred rangesuch as 5-25 is given, this means preferably at least 5 and preferablynot more than 25.

With reference to FIG. 2 there is shown a top or plan view of aself-adhesive reinforced foam gasket 25 of the present invention havinga top surface 26, which is the top surface of the flexible foam layer 32shown in FIG. 3. Gasket 25 is shown as circular, but it can be any othershape as known in the art, particularly the shapes used in automotiveapplications.

With reference to FIG. 3 there is shown in cross-section a self-adhesivereinforced foam gasket 30 of the present invention. Gasket 30 comprisesa release liner 40 comprising release paper 42 having a release(preferably silicone) coating 38 which provides a release surface. Thusrelease liner 40 has an upper surface which is a release surface. Therelease paper is preferably 40-160 lb., more preferably 60-100 lb., morepreferably about 78 lb., clay-coated, long-fiber, super-calandered,flat, heat resistant paper as known in the art. Plastic or polymericfilm may be substituted for paper layer 42. A layer of pressuresensitive adhesive 36 is applied to the release surface of the siliconerelease coating 38. The pressure sensitive adhesive (PSA) layer 36 ispreferably a high-temperature rubber-based hot melt pressure sensitiveadhesive such as from Monsanto or National Starch that is heated so thatit can be extruded onto the release liner. Other pressure sensitiveadhesives, particularly high-temperature PSAs, known in the art can beused, such as PSAs which are 100% solids (such as silicone-based) andPSAs which have a solvent carrier which is preferably an organic liquid,less preferably water, which is evaporated after the PSA layer isapplied. PSA layer 36 is preferably 0.5-5, more preferable 1-3, morepreferably about 2, mils thick. The PSA is selected such that it canwithstand the heating process described hereinafter and can effectivelybond to the intended substrate, which is preferably a part of anautomobile, commonly a plastic part of an automobile.

Next, a layer of flexible polymeric film 34, preferably polyester film,is applied to the PSA layer 36. Flexible polymeric film layer 34 ispreferably 0.5-4, more preferably 0.7-2, more preferably 0.8-1.5, morepreferably about 1, mil thick polyester film (preferably nontreated),such as Mylar brand polyester film from DuPont. Other flexible polymericfilms having the strength, flexibility and temperature resistance ofMylar may also be used, such as PET polymeric film, polyvinylidenechloride polymeric film, polyacrylic film, polyvinyl chloride film,polyvinyl acetate film, polyamide film, and polyimide film. Flexiblepolymeric film layer 34 provides reinforcement to the gasket andprevents migration of plasticizer from flexible foam layer 32 topressure sensitive adhesive layer 36, where it would adversely affectand degrade the PSA.

To the polymeric film layer 34 is thermally bonded a layer of flexiblefoam 32, preferably closed cell PVC flexible foam, less preferably otherPVC foams such as lower temperature PVC foams and polymeric PVC foams,alternatively other flexible foams such as polyurethane foam,polyethylene foam, other vinyl foams, and polypropylene foam. Aftercuring and solidifying, the flexible foam layer 32 is preferably{fraction (1/32)} to 1 inch thick, more, preferably {fraction (1/16)} to¾ inch thick, more preferably ⅛ to ½ inch thick, more preferably{fraction (3/16)} to ¼ inch thick.

The pressure sensitive adhesive layer 36 is applied to the releasesurface of the release liner 40 in a conventional manner, such as byslot die extrusion. The polymeric film layer 34 is then laminated orapplied and adhered to the PSA layer 36 in a conventional manner.Preferably, the flexible foam layer 32 is then provided and thermallybonded to the polymeric film layer 34 by providing the flexible foam ina liquid, uncured state (with blowing agent) on the polymeric film in arelatively thin layer and then heating or baking the material in an ovento activate the blowing agent, expand and cure the flexible foam andsimultaneously thermally bond the flexible foam to the polymeric film34.

A preferred flexible plastic or polymeric foam is closed cell PVC foam,made of about 34 parts PVC dispersion resin such as Kaneka Prod. No.EH219, about 8 parts PVC blending resin such as Kaneka Prod. No. PBMB5F, about 39 parts phthalate plasticizer (88% phthalate plasticizer,12% chlorinated paraffin), about 14 parts CaCO₃ filler, about 4 partsazodicarbonamide blowing agent, about 0.5 parts cell stabilizer such asProduct VS103 from Air Products, about 0.5 parts heat stabilizer such asa zinc blend such as Ferro Prod. 5573, and about 0.5 parts epoxidizedsoybean oil plasticizer. Less preferably these amounts may be changed±10%. Other components and optional ingredients known in the art mayalso be used. Substitute components known in the art may be used.

The expanded and cured flexible foam or PVC flexible foam preferably hasa density of 5 to 5.5 to 6 to 7 to 8 to 9 to 10 to 12 to 15 to 20 lb/ft³more preferably 6-8 or 7-8 lb/ft³. The flexible foam and PVC flexiblefoam preferably meets or exceeds the following requirements orspecifications which are known in the art: GM 6086M Type 1A, GM 6086Type 1B, GM 6086 II, MSAY-505, MS-AY511, ESB-M3G101-A Type 1,ESB-M3G77-A, and ESB-M3G102-A.

With reference to the preferred PVC formulation above, at roomtemperature the liquids are mixed and the powders are then blended in toyield a PVC plastisol, which is a liquid flexible foam precursorincluding a blowing agent. The substrate, which is the release liner 40with PSA layer 36 and polymeric film layer 34, is provided in a sheetpreferably about 5 feet wide (less preferably at least 4, 3, 2 or 1 footwide) and preferably at least 20, 50, 100, 200 or 300 feet long, rolledup. The substrate is slowly unrolled and the liquid PVC plastisol orflexible foam precursor with blowing agent, at room temperature, is castor transferred or applied or provided in an appropriate thickness orlayer to the polymeric film surface with a knife or similar coater. Thesubstrate with PVC plastisol or flexible foam precursor is thentransported into an oven where it is heated or baked at preferably about400° F., less preferably about 380-420° F., for preferably about 3.5min., less preferably about 3 to 4 minutes, to activate the blowingagent, to expand and cure the precursor and solidify the flexible foamand thermally bond it to the polymeric film layer 34. This operationyields a cured flexible foam layer which is thermally bonded to thepolymeric film layer. If other liquid plastisols or flexible polymericfoam precursors are applied to the polymeric film surface, the time andtemperature parameters are adjusted as known in the art to effectivelyexpand and cure the flexible foam and thermally bond it to the polymericfilm. The product is then removed from the oven and permitted to cool toroom temperature. As a result of this operation the flexible foam layeris thermally bonded to the polymeric film layer.

As a result of the above procedure, the top surface 26 of the flexiblefoam will have an “as cast” appearance. This top surface 26 is not anadhesive surface and is produced such that it will not stick to othersurfaces. If through some error top surface 26 is tacky or sticky, arelease coating such as silicone may be applied thereto or to the bottomsurface 27 of release liner 40 to permit the product to be rolled orcoiled up. The thermal bond between the flexible foam 32 and thepolymeric film 34 is preferably such that the flexible foam itself willtear before the thermal bond will yield. Thus the bond strength isgreater than the tear strength or tensile strength of the flexible foam.

The product is preferably produced as a sheet or length of material 50(as shown in FIG. 4) about 5 feet wide and about or at least 20 to 50 to100 to 200 to 300 feet long, depending on the thickness of the product,which length of material is suitable for die-cutting a self-adhesivereinforced foam gasket therefrom. The product or length of material 50is rolled up, typically into a roll or coil 2-3 feet in diameter. Thusthe thicker the material, usually the shorter the length, so that thepreferred diameter of the roll or coil is not exceeded. The rolls orcoils of the product are then provided to a die-cutting operation whichdie cuts the gaskets therefrom. The product may be slit and provided tothe die-cutting operation in rolls less than 5, 4, 3, 2 or 1 feet wide,sometimes as narrow as 8-10 inches wide (thus at least 8 or 10 inches or1, 2, 3 or 4 feet wide). The die-cutting operation produces via aconventional die-cutting procedure a die-cut self-adhesive reinforcedfoam gasket, preferably for the automotive industry, such as a gasketfor inside the glove box, for the outside mirror, around where the seatbelt attaches to the floor, as a seal around the top of the fuel tankfilling tube, around audio speakers in the front and back of the car,around cut-outs in the dash for air conditioning ducting, around theinside of the door, to act as a secondary seal around the opera window,and to act as a secondary seal around the trunk lid. It is also known inthe art other places on the automobile where self-adhesive foam gasketssuch as described herein are used. As is apparent, the invented gasketmaterial can be used in similar gasket applications outside theautomotive industry. These gaskets principally cushion and seal againstwind, noise and moisture.

These gaskets may be shaped as circles (see FIG. 2), squares,rectangles, figure-eights, and all sorts of other shapes known in theart, typically with most of the central area cut out leaving a perimeterwall typically ⅛ to ¼ to ½ to ¾ to 1 to 2 to 4 inches wide (which may ormay not have cut out holes for fasteners). Alternatively the gasket mayhave only small cut outs for bolt or screw or fastener holes etc.Alternatively the gasket may be a strip ⅛ to ¼ to ½ to ¾ to 1 to 2 to 4inches wide with or without cut out holes for fasteners, etc.

To apply the gasket, the release liner is removed and the gasket isapplied and pressed into position.

Although particular embodiments of the invention have been described indetail, it is understood that the invention is not limitedcorrespondingly in scope, but includes all changes and modificationscoming within the spirit and terms of the claims appended hereto.

What is claimed is:
 1. A method of making a length of material suitablefor die-cutting a self-adhesive reinforced foam gasket therefrom, saidmethod comprising the steps of (a) providing a substrate having arelease liner, a layer of pressure sensitive adhesive and a layer offlexible polymeric film, said release liner having an upper surfacewhich is a release surface, said pressure sensitive adhesive layeradhering to said release surface, said flexible polymeric film layeradhering to said pressure sensitive adhesive layer, and (b) providing alayer of liquid flexible foam precursor including a blowing agent ontosaid flexible polymeric a film layer, heating said flexible foamprecursor, activating said blowing agent and expanding and curing saidflexible foam precursor to yield a cured flexible foam layer which isthermally o bonded to said flexible polymeric film layer to yield alength of material suitable for die-cutting a self-adhesive reinforcedfoam gasket therefrom, said flexible foam being polyvinyl chlorideflexible foam having a density of at least 5 lb/ft³, said flexible foamlayer contacting said flexible polymeric film layer, said thermal bondbetween said flexible foam layer and a said flexible polymeric filmlayer being greater than the tear strength of said flexible foam, saidflexible polymeric film layer being effective to inhibit leaching ofplasticizer from said flexible foam layer into said pressure sensitiveadhesive layer, said flexible polymeric film layer and said flexiblefoam layer being separate, distinct layers made of different materials.2. A method according to claim 1, wherein said flexible polymeric filmis polyester film.
 3. A method according to claim 1, wherein saidflexible foam is closed cell polyvinyl chloride flexible foam.
 4. Amethod according to claim 1, wherein said cured flexible foam layer is{fraction (1/16)} to ¾ inch thick.
 5. A method according to claim 1,wherein said flexible polymeric film layer is 0.5 to 4 mils thick.
 6. Amethod according to claim 1, wherein said cured flexible foam layer hasa density of 5 to 20 lb/ft³.
 7. A method according to claim 1, whereinsaid length of material is at least one foot wide and at least fiftyfeet long.
 8. A method according to claim 1, wherein said pressuresensitive adhesive is a high-temperature pressure sensitive adhesive. 9.A method according to claim 1, wherein said pressure sensitive adhesiveis a high-temperature hot melt pressure sensitive adhesive.
 10. A methodaccording to claim 1, wherein the liquid flexible foam precursor is aliquid polyvinyl chloride plastisol.
 11. A method according to claim 1,wherein said flexible foam precursor is heated in an oven at about380-420° F. to activate the blowing agent and expand the precursor. 12.A method according to claim 1, wherein said flexible foam precursor isheated in an oven for about 3 to 4 minutes to activate the blowing agentand expand the precursor.
 13. A method according to claim 1, whereinsaid length of material is at least 4 feet wide and east 200 feet long.14. A method according to claim 1, further comprising the step ofproviding at least a portion of said length of material to a die-cuttingmachine and die-cutting a self-adhesive reinforced foam gaskettherefrom.
 15. A method according to claim 1, further comprising thestep of providing a release coating on a surface selected from the groupconsisting of a top surface of said flexible foam layer and a bottomsurface of said release liner.
 16. A method according to claim 7,further comprising the step of slitting said length of material prior toa die-cutting operation.
 17. A method according to claim 1, said methodconsisting essentially of said steps (a) and (b).
 18. A method accordingto claim 1, said length of material being at least eight inches wide andat least twenty feet long.